Degradation kinetics and mechanism of penicillin G in aqueous matrices by ionizing radiation

Highlights: • Gamma radiation was effective to degrade penicillin G in aqueous solution. • Radiation combined with Fenton oxidation enhanced mineralization of penicillin G. • The presence of peptone and glucose inhibited the degradation of penicillin G. - Abstract: The gamma radiation induced-degradation of a β-lactam antibiotic, penicillin G was investigated in aqueous solution. Special attention was paid to the effects of the organic substances such as peptone and glucose on penicillin G degradation, which can be found in the wastewater of the factories producing antibiotics. Results showed that gamma radiation was effective to degrade and deactivate penicillin G in pure water. With the initial concentrations of 0.27 mM, 1.34 mM and 2.68 mM, a complete removal of penicillin G could be achieved at the adsorbed doses of 2.5 kGy, 10 kGy and 20 kGy, respectively. Penicilloic acid from the β-lactam ring cleavage and a series of fragment compounds such as thiazolidine and penicillic acid were identified during gamma irradiation-induced degradation of penicillin G. Addition of Fe²⁺ was efficient to enhance the mineralization. The TOC removal efficiency of penicillin G was 21.7% using gamma irradiation alone at 10 kGy, which increased to 56.4% with 1.0 mM Fe²⁺ addition. The gamma radiation-induced degradation of penicillin G was inhibited in the presence of peptone and glucose and the inhibitive effect increased with increasing their concentrations. The rate constant, k of the pseudo first-order kinetics decreased by 74% and 64% in the presence of 1.0 g/L of peptone and glucose, respectively, and by 96% and 89% in the presence of 10 g/L of peptone and glucose, respectively. The ratio of k/k₀ was increased by 1.3 times with H₂O₂ addition and by 3 times with Fe²⁺ addition, in the presence of 10 g/L of glucose. Adding Fe²⁺ was effective to improve the ionizing radiation induced degradation of penicillin G antibiotic in the glucose-containing wastewater.